Internet radio outfit Slacker detected a touch of gray in its service last year. The retro/biker dashboard player for Web and mobile listeners essentially had gone unchanged since the San Diego company was founded in 2006.

So in February, Slacker revamped its appearance — going modern and graphic with its Web/mobile player and display screen, as well as tweaking some subscription options to answer what rivals such as Spotify were bringing to market.

Since the relaunch of Slacker in mid-February, the company says more than 6 million new listeners have joined, including 3.5 million on mobile, for a total of 35 million listeners. The average listening time has swelled 25 percent, and it has more than 100,000 new paid subscribers.

Slacker, with a library of 13 million songs, has been keeping the competitive pressure on Pandora — its larger, most comparable rival. It has added sports from ESPN and news from ABC to its core music offerings. It has DJs who put together stations. Slacker has distribution deals with every major North American wireless operator. And it is available in vehicles from Ford, GM, Chrysler, Honda, Subaru and Tesla.

Slacker’s Chief Executive Jim Cady talked with U-T San Diego about the company’s “freemium” business model, its new look and competitive vibe in today’s Internet radio/online music marketplace. Here are some excerpts.

Q: What was the goal of changing the Slacker interface?

A: We had really built our service for the core music fan. While we want to satisfy those customers, it didn’t have the simplicity that was required for mainstream. As a result, we came out and built something that is much more graphically oriented, easier to use and kind of uncovers some of those hidden gems from a features standpoint.

Q: What hidden gems?

A: One of them is what we call Fine Tune; the ability for somebody to adjust content without having to go through a bunch of steps. They can say, I want to listen to more popular music on this station versus less popular music. Or I want to be able to have newer stuff as opposed to older stuff, or I want to discover more and not necessarily just get the hits.

Q: What else is cool about the new look?

A: One of the things we have launched more actively recently is countdown stations. Recently we launched 101 greatest classic rock songs. It is highly curated by a famous rock DJ called Red Beard. It has a lot of interviews. And the interesting thing is we have seen listenership go up dramatically. The average listening time on a station is about 29 minutes. We’re seeing 79 minutes on this station.

Q: How many subscribers do you have?

A: We don’t release a specific number, but we give a range. We have between 500,000 and 1 million paid subscribers.

Q: Where are subscribers coming from?

A: A vast majority of them are coming from mobile. But the interesting thing is we’re seeing customers more and more starting to listen on multiple platforms. So my main listening platform is mobile. But I’m also listening on the Web, or on the Xbox at home.

Q: This is a very competitive business. How do you stand out?

A: Our focus will remain on radio and the ability to personalize that radio as opposed to an on-demand focus. While we do that, we look at that as an adjunct to radio because we think most people are passive listeners. They like music. They know what they like. They want to be able to adjust it a little bit. But they don’t want to sit down and build everything from the ground up.

So we use not only machine learning but we also have 75 people who program content who are experts in their specific areas of music.

Q: You have many free users. How do you make them subscribers?

A: It is a delicate balance. In our case, whether you’re a free listener or a paid listener — this is different for us than many of our competitors — you are contributing to us. All of these customers — free or paid — are gross margin positive.

So while we would love to have everybody be a paid subscriber, we realize that is not likely to be the case. We have got to finely balance the fact that if you’re a free listener, we don’t want to make it such an awful experience that you’re going to say, ‘Hey, I either subscribe or I go away’ because at the end of the day we want you.

Q: But what would compel free users to begin paying?

A: We spend a lot of time on this every day — what levers can we use to get you to subscribe other than getting rid of the ads? Being able to skip an unlimited number of songs if I pay, that is a big thing for customers. I can only skip six times on the free service.

A lot of people on mobile have concerns about their data plan. The ability to store content offline is a big thing for the paid service that isn’t available to the free user. So there are some very compelling features to get people to move over.

Q: What’s next for Slacker?

A: One of the reasons we focused heavily on mobile and working with the carriers is because it’s a growing segment of the business, which is great for us in the short term.

But in the midterm, we view mobile as the gateway to the car. And that is obviously one of the platforms we really want to win.

We already have deals with Ford, Chrysler, GM, Honda, etc. We think that mobile footprint helps position us for the car going forward.